Mixer seal

ABSTRACT

A mixer is disclosed of the type including a vessel and a motor shaft extending upwardly through a bottom wall of the vessel and carrying an agitator at its upper end. A seal is provided between the shaft and bottom wall. The motor is mounted on a plate beneath the vessel and the interior surface of the bottom wall of the vessel is machined parallel to the plate. The seal includes a sleeve which surrounds the shaft and is supported upon the machined surface. The sleeve carries a stationary sealing member having a flat surface parallel to the machined surface and perpendicular to the shaft. A second sealing member rotates with the shaft and includes a flat face spring-urged into engagement with the face of the stationary member. A method is disclosed for establishing the perpendicular relationship of the sealing surfaces and shaft axis. The method includes the step of grinding the inner surface of the bottom wall parallel to the motor mounting plate by means of a grinding wheel driven by a motor mounted on the plate.

United States Patent [1 1 a [451 Nov. 27, 1973 Guary 1 MIXER SEAL [76] Inventor: Gabriel Guary, 23, rue du Conseiller Collignor, Paris, France [22] Filed: July 12, 1972 [21] Appl. No.: 271,074

[52] U.S. Cl. 259/108, 259/D1G. 16 [51] Int. Cl. F16j 15/28, Fl6j 15/30 [58] Field of Search 259/DlG. 16, 107, 259/ 108 [56] References Cited UNITED STATES PATENTS 1,666,013 4/1928 Jackson 259/DIG.16 2,627,171 2/1953 Brumagim.. 259/DIG. 16 2,867,997 1/1959 Lake 259/DIG. 16 2,911,240 11/1959 Boutros et a1. 259/D1G. 16

Primary Examiner-William 1. Price Attorney-James S. Hight et a1.

[57] ABSTRACT A mixer is disclosed of the type including a vessel and a motor shaft extending upwardly through a bottom wall of the vessel and carrying an agitator at its upper end. A seal is provided between the shaft and bottom wall. The motor is mounted on a plate beneath the vessel and the interior surface of the bottom wall of the vessel is machined parallel to the plate. The seal includes a sleeve which surrounds the shaft and is supported upon the machined surface. The sleeve carries a stationary sealing member having a flat surface parallel to the machined surface and perpendicular to the shaft. A second sealing member rotateswith the shaft and includes a flat face spring-urged into engagement with the face of the stationary member.

A method is disclosed for establishing the perpendicular relationship of the sealing surfaces and shaft axis. The method includes the step of grinding the inner surface of the bottom wall parallel to the motor mounting plate by means of a grinding wheel driven by a motor mounted on the plate.

5 Claims, 7 Drawing Figures MlXlElR ssxr.

BACKGROUND OF THE iNVENTION This invention relates to mixers and is particularly directed to mixers of the dispersion mill type. At the present time, many different types of mixers and dispersion mills have been proposed for carrying out such operations as the dispersion of fine pigments in vehicles and solvents during the production of paints, printing inks, lacquers and the like. Dispersion mills of this type are also utilized in connection with the emulsion of liquids and the dissolution of various types of gums, resin particles and the like. These dispersion mills include a vessel and an agitator which is rotated within the vessel at a high speed, for example, at a peripheral speed of 10,000 feet per minute.

In the past, it has been recognized that there would be substantial advantages in mounting the impeller upon a shaft extending upwardly from the bottom wall of the mixer. Such a bottom drive greatly simplifies the construction of the top closure of the mixer, thereby facilitating the provision of means for operating the mixer under vacuum or pressure. However, in practice, a substantial amount of difficulty has been encountered in providing a reliable leakproof seal surrounding such a high-speed shaft extending upwardly into the mixer. As a result, most commercial mixers still employ a motor mounted on top of the mixer where the sealing problem is eliminated, but the other attendant disadvantages are present.

The principal object of the present invention is to provide a novel seal for sealing an opening in the bottom wall of a high-speed mixer surrounding an agitator shaft which extends upwardly into the mixer.

Another object of the present invention is to provide a reliable seal which is relatively inexpensive to produce and which requires only a minimum amount of maintenance during protracted periods of usage.

Still another object of the present invention is to provide a method for economically fabricating such mixer seals.

More particularly, the present invention is predicated upon the concept of providing a mixer seal including a stationary member surrounding the agitator shaft and having an upper face positioned perpendicular to the axis of the agitator shaft. The upper face of the stationary member is in flat facial engagement with a rotating sealing member carried by the agitator shaft. The rotating sealing member revolves with the shaft and is spring-urged into engagement with the stationary memher.

In accordance with the present invention, the desired perpendicularity of the sealing surfaces and the agitator shaft is obtained by providing a mounting plate for the motor beneath the mixer vessel and by machining a supporting surface on the interior of the bottom wall of the mixer parallel to this plate. When the motor is mounted upon the plate, the axis of the shaft is perpendicular to the plate and, hence, perpendicular to the machined surface on the inner wall of the tank.

The seal includes a sleeve having an upper flange positioned against this machined surface. The sleeve in turn has an enlarged upper bore including a shoulder parallel to the flange seating surface. The stationary ring is seated within this upper recess and includes a radial'flange which compresses an O-ring against the recess. As a result, when a pressure is applied to the face of the stationary ring by the rotating ring, the surface of the stationary ring assumes a position parallel to the machined surface of the tank bottom wall and, hence, perpendicular to the axis of the shaft. The rotating sealing ring is supported upon the shaft by means of an O- ring. A spring is compressed between this ring and the agitator mounting hub. The spring is effective both to urge the rotating ring toward the stationary ring and to cause the rotatingring to rotate with the shaft. Consequently, the rotating ring is free totilt relative to the shaft and, hence, assumes a position in which its flat face is in complete contact with the flat face of the stationary ring and the plane of their contact is perpendicular to the axis of the shaft.

A further aspect of the present invention is to provide a method for economically fabricating such seals. In accordance with the present method, the vessel is initially inverted with the bottom wall and its opening uppermost. A base assembly including the motor mounting plate with the motor in place is positioned over the vessel and is lowered so that the motor shaft extends through the opening. This base is then welded to the vessel. Thereafter, the motor is removed and is replaced by a grinding wheel motor. having a shaft extending through the opening in the bottom wall. A flat disc grinding wheel is mounted on the end of the shaft and is utilized to grind the interior of the portion of the bottom wall surrounding the opening parallel to the motor mounting plate. This ground surface is perpendicular to the grinding wheel shaft and will be perpendicular to the motor shaft when it is in place.

When this operation is completed, the grinding wheel and its motor are removed and the main mixer motor is permanently mounted. Thereafter, the mixer vessel is turned upright and the sealing sleeve is placed over the motor shaft and tightened against the lower wall of the mixer. The shoulder of the sleeve is thus disposed parallel to the machined surface of the tank wall and parallel to the motor mounting plate and,.hence, perpendicular to the motor shaft. The stationary ring is inserted in the enlarged bore and the rotating ring together with its spring and hub are placed over the end of the shaft and tightened into place.

The spring pressure forces the stationary ring toseat with its surface perpendicular to the axis of the shaft and the cooperating surface of the rotating ring automatically assumes a position in parallel facial contact. As a consequence, the rotating contact between the stationary and rotating rings occurs in a plane truly perpendicular to the axis of the shaft and an even pressure distribution is achieved over the entire sealing surfaces resulting in a highly leakproof, long-lasting seal.

These and other objects and advantages of the present invention will be more readily apparent from a consideration of the following detailed description of the drawings illustrating a preferred form of seal and the method of its fabrication.

DESCRIPTION OF THE DRAWINGS H6. 1 is a perspective view of one formof mixer embodying the present seal construction.

FIG. 2 is a vertical cross-sectional viewthrough the bottom wall of the mixer, the seal and motor mounting plate.

FIG. 3 is a semi-diagrammatic view, partially in section,showing the initial step in seal fabrication, i.e.,

bringing the base and motor into assembled relationship with an inverted mixing vessel.

FIG. 4 is a view similar to FIG. 3 showing the base welded to the mixer vessel.

FIG. 5 is a view similar to FIG. 3 showing a grinding operation being performed on the inner surface of the tank bottom wall.

FIG. 6 is a view similar to FIG. 3 showing the motor being secured in position prior to the final seal assembly.

FIG. 7 is a diagrammatic view, partially in section, showing the mixer in an upright position with the seal completely assembled.

DESCRIPTION OF THE PREFERRED EMBODIMENT One form of mixer 10 embodying the present seal is illustrated in FIG. 1. As there shown, the mixer includes a generally cylindrical vessel 11 surrounded by a cooling or heating jacket 12. It is to be understood thatthe upper portion of vessel 11 is provided with any suitable form of cover 13 including a vacuum-tight cover if desired. The vessel is also provided with any suitable form of material discharge valve desired. Jacket 12 is fitted with suitable connections for circulating water or other heat exchange liquid in the annular space defined by the heating jacket surrounding the walls of vessel 11. These details of construction are well known in the prior art and constitute no part of the present invention.

As shown in FIG. 1, vessel 11 is supported upon a base member 14 including arcuate legs 15. The upper ends of these legs are welded or otherwise secured to the double curved bottom wall 16 of vessel 11, while the lower portions of the legs are secured to a floorengaging base plate 17. Base 14 also includes a transverse mounting plate 18 which is welded or otherwise joined to legs and extends transversely of the base assembly beneath the vessel 11 in a direction generally parallel to base plate 17.

Transverse mounting plate 18 carries an electric motor 20, the flange of which is bolted to the undersurface of the base plate as by means of bolts 211. The shaft 22 of motor extends upwardly into the vessel ill through an opening 23 formed in the bottom wall 116 of the vessel. The upper end of shaft 22 is beveled as at 24 and carries an impeller 25 of any suitable configuration. This agitator cooperates with stationary vertical baffles (not shown).

As shown in FIG. 2, impeller 25 is seated against a hub member 26, the hub member having a frustoconi- I cal opening which receives the tapered end 24 of shaft 22. The hub is rotated with the shaft by means of the interengagement of a key 27 disposed within aligned slots in theshaft and hub. The upper end of hub 26 includes an annular flange 28 surrounding an upstanding rim 30. The flange also carries a plurality of upstanding pins 31 which are received within corresponding apertures in impeller 25. The impeller is locked in place against the hub flange 28 by means of a nut 32 which engages a threaded extension 33 of shaft 22. Again, the details of mounting of the impeller upon shaft 22 are well known and constitute no part of the present invention.

' The novel feature of the mixer shown is the seal 35 which provides a fluidtight seal between shaft 22 and the surrounding bottom wall 16 of the vessel. The details of this seal are best shown in FIG. 2. As there shown, the seal includes a sleeve member 36 which extends downwardly through opening 23, the opening being larger than the outside diameter of the sleeve to provide peripheral clearance surrounding the sleeve.

Sleeve member 36 is provided with a radially extending flange 37 adjacent to its upper end. This flange overlies a portion of wall 116 surrounding opening 23. An annular gasket 38 is compressed between the undersurface of flange 37 and an upper machined surface 40 of bottom wall 16. As is explained in detail below, surface 40 is ground so as to be parallel to the undersurface 41 of mounting flange 18. The undersurface of flange 37 is thus also parallel to the machined under-- surface 41 of mounting plate 18 and is perpendicular to the axis of shaft 22. The outer surface of the cylindrical portion'44 of sleeve 36 is threaded and is engaged by lock nuts 45 and 46 which clamp the sleeve against bottom wall 16 of the mixer. A gasket 47 is interposed between upper lock nut 45 and the bottom wall 16.

Sleeve 36 is provided with an internal bore 48 of appreciably larger diameter than the outer diameter of shaft 22. The upper portion of bore 48 is enlarged as at 50 to form a shoulder 51 surrounded by cylindrical wall 52. Shoulder 51 is machined parallel to the annular undersurface of flange 37. A graphite ring member 53 is disposed within enlarged bore portion 50. The ring 53 includes a radially extending flange 54 and a depending annular portion 55 in engagement with an O- ring 56 which is compressed between flange 54, shoulder 51 and wall portion 52 of the sleeve member. The graphite member 53 is provided with a central bore appreciably larger than shaft 22. The ring 53 is held stationary by the frictional engagement of O-ring 56.

When O-ring 56 is compressed, the axis of graphite ring 53 is maintained concentric with the axis of shaft 22. The upper annular surface 58 of the graphite ring is machined perpendicular to the axis of the bore through the ring and, hence, is perpendicular to the axis of shaft 22. Surface 58 engages a cooperating flat surface 60 formed on the bottom of a rotating sealing ring 61 which is preferably formed of a suitable bearing steel.

Rotating member 61 is provided with an internal channel 62 which houses an O-ring 63 compressed between the surrounding walls of channel 62 and a cylindrical portion of shaft 22. Rotating member 61 also is provided with a recess 64 in its upper face which receives the lower end of a compression spring 65. It is to be understood that the bore through ring 61 is larger than the outer diameter of shaft 22 so .that the ring can tilt slightly to accommodate itself to the surface 58 of stationary ring 53. Ring 61 is caused to rotate with the shaft by the engagement of the lower end of spring 65 in a transverse slot 66 formed in the rotating member. The upper end of spring 65 is similarly received in a slot 67 formed in the lower wall of hub member 26.

Spring 65 is effective to maintain a sealing pressure between opposed faces 58 and 60 of the stationary graphite sealing member and rotating sealing member, respectively. This pressure is preferably between I and 2 kilograms per square centimeter. The present seal is effective to prevent leakage along the shaft 22 or through the bottom wall of the tank during a mixing operation. The seal requires no lubrication and can be utilized for substantial periods of time without replacethe opening being appreciably larger than the diameter of shaft 22 of motor 20. The base assembly 14 is prefabricated with legs 15 joined to base plate 17 and to transverse mounting plate 18. Motor 20 is temporarily bolted to mounting plate 18. The assembled motor and base structure are then placed over the inverted vessel and lowered into position with the motor shaft 22 being substantially centered within opening 23. As shown in FIG. 4, the base assembly is then welded to the bottom wall 16 of the tank in such a position that the motor shaft extends through bottom wall opening 23.

I In the next operation, motor 20 is disengaged from mounting plate 18 and a suitable grinding motor 70, such as an electric or pneumatic motor, is bolted to plate 18 in place of mixer motor 20. Motor 70 is provided with a shaft 71 which extends through opening 23 in the bottom wall and carries on its outer end a cylindrical grinding wheel 72 having a flat upper grinding face 73. Face 73 is disposed in engagement with the inner surface of wall 16 and is effective to grind surface 40 in a plane perpendicular to the axis of shaft 71 and parallel to surface 41 of mounting plate 18.

After surface 40 has been ground, grinding wheel 72 is removed and motor '70 is disengaged from plate 18. Thereafter, motor 20 is again bolted to plate 18 with the motor shaft 22 extending through opening 23, the axis of this shaft now being perpendicular to ground surface 40. Nuts 45 and 46 and gasket 47 are placed over the shaft prior to the mounting of motor 20.

In the final assembly, the hub and base are turned right side up and gasket 38, sleeve 36, O-rings 56 and 63, stationary graphite ring 53, and rotatable steel ring 61 are placed over the end of shaft 22. Sleeve 36 is secured in place against wall 16 by tightening lock nuts 45 and 46. r

Thereafter, spring member 65 is placed over shaft 22 together with hub 26 and impeller 25. These elements are thereafter locked in position by tightening nut 32. When this nut is tightened, the proper compressive force of between 1 and 2 kilograms per square centimeter is applied through spring 65 to the upper surface of rotating member 61. This spring thus controls the pressure between cooperating rotating seal faces 58 and 60. Since surface 40 is disposed perpendicular to the axis of shaft 22, shoulder 51 is also perpendicular to the axis of the shaft. Consequently, when graphite ring 53 is forced downwardly against O-ring 56, the upper surface 60 of the graphite sealing member assumes aposition in a plane perpendicular to the axis of rotation of shaft 22.

The upper ring 61 is supported only by O'ring 63 and spring 65. Thus, this upper rotating ring automatically assumes a position with its lower surface 60 lying parallel to the upper surface 58 of the graphite ring. As the shaft 22 rotates, the surfaces 58 and 60 thus are subjected to a substantially even pressure across their surfaces since they meet in a plane perpendicular to the axis of the rotating shaft.

From the above disclosure of the general principles of the present invention and the description of a pre ferred embodiment, those skilled in the art will readily comprehend various modifications to which the invention is susceptible. Therefore, I desire to be limited only by the scope of the following claims.

Having described my invention, I claim:

1. In a mixer of the type including a base, a vessel having a bottom wall, a motor having a shaft extending upwardly through an opening in the bottom wall, and an impeller mounted upon said shaft, the invention which comprises:

a plate carried by said base and disposed beneath said.

bottom wall; i

said motor having a flange mounted in abutment with a surface of said plate; I

a machined surface on the interior of the bottom wall of said vessel extending parallel to said surface of said plate; a

a seal for the opening in said bottom wall; V

said seal comprising a sleeve having an internal bore surrounding said shaft, said bore being of greater diameter than said shaft to provide a clearance therebetween;

said sleeve further including a'radial flange on its upper end disposed above and supported by said machined surface, said sleeve extending downwardly through said opening;

a stationary sealing ring having a bore receiving said shaft;

means for supporting said sealing ring with said sleeve adjacent to the upper end thereof;

said stationary sealing ring having; an upper surface disposed perpendicular to the axis of said shaft;

a rotating sealing ring surrounding said shaft and being carried thereby, said rotating sealing ring having a lower surface in flat face-to-face engagement with the upper surface of said stationary ring;

spring means urging said rotating sealing ring into engagement with said stationary sealing ring; and

means for causing said rotating sealing ring to rotate with said shaft.

2. The seal of claim 1 in which the rotating ring is steel and the stationary ring is graphite.

3.'The seal of claim 1 in which said last-named means comprises a transverse slot in said rotating ring in engagement with the lower end of said springfand a hub secured to the upper end of said shaft, said hub having a transverse slot receiving the upper end of said spring.

4. The seal of claim 3 in which said rotating ring includes:

an internal channel;

an O-ring disposed within said channel, said O-ring being compressed between said channel and said shaft and together with said spring providing the only support for said rotating ring.

5. The seal of claim 1 in which said sleeve has an enlarged bore adjacent to its upper end including a shoulder parallel to the undersurface of the radial flange on said sleeve, the stationary ring including a radial flange having an undersurface parallel to the upper surface of said ring, and an O-ring compressed between the flange on said stationary ring and the shoulder of said sleeve.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,774,889 Dated November 27, 1973 Inventor(s) Gabriel Guary- It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 31. change "with to within Signed and sealed this 23rd day of April 197M.

(SEAL) Attest:

EDWARD ILFLETCHEILJR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. In a mixer of the type including a base, a vessel having a bottom wall, a motor having a shaft extending upwardly through an opening in the bottom wall, and an impeller mounted upon said shaft, the invention which comprises: a plate carried by said base and disposed beneath said bottom wall; said motor having a flange mounted in abutment with a surface of said plate; a machined surface on the interior of the bottom wall of said vessel extending parallel to said surface of said plate; a seal for the opening in said bottom wall; said seal comprising a sleeve having an internal bore surrounding said shaft, said bore being of greater diameter than said shaft to provide a clearance therebetween; said sleeve further including a radial flange on its upper end disposed above and supported by said machined surface, said sleeve extending downwardly through said opening; a stationary sealing ring having a bore receiving said shaft; means for supporting said sealing ring with said sleeve adjacent to the upper end thereof; said stationary sealing ring having an upper surface disposed perpendicular to the axIs of said shaft; a rotating sealing ring surrounding said shaft and being carried thereby, said rotating sealing ring having a lower surface in flat face-to-face engagement with the upper surface of said stationary ring; spring means urging said rotating sealing ring into engagement with said stationary sealing ring; and means for causing said rotating sealing ring to rotate with said shaft.
 2. The seal of claim 1 in which the rotating ring is steel and the stationary ring is graphite.
 3. The seal of claim 1 in which said last-named means comprises a transverse slot in said rotating ring in engagement with the lower end of said spring; and a hub secured to the upper end of said shaft, said hub having a transverse slot receiving the upper end of said spring.
 4. The seal of claim 3 in which said rotating ring includes: an internal channel; an O-ring disposed within said channel, said O-ring being compressed between said channel and said shaft and together with said spring providing the only support for said rotating ring.
 5. The seal of claim 1 in which said sleeve has an enlarged bore adjacent to its upper end including a shoulder parallel to the undersurface of the radial flange on said sleeve, the stationary ring including a radial flange having an undersurface parallel to the upper surface of said ring, and an O-ring compressed between the flange on said stationary ring and the shoulder of said sleeve. 